Hydrophilic silicones

ABSTRACT

Curable silicon prepolymers are made hydrophilic after cure by mixing the prepolymer with ethoxylated nonionic surface active agent or cationic or amphoteric fluorochemical surface active agent. The cured silicones have semipermanent hydrophilicity and are especially useful as dental impressions.

TECHNICAL FIELD

This invention relates to curable silicone prepolymer compositions andcured silicone polymers. In another aspect, this invention relates tomolded silicone articles. In a further aspect, this invention relates todental impression materials.

BACKGROUND ART

Many different substances have been used as dental impression materials,each having its own advantages and disadvantages. An impression materialmust undergo a transformation, while in the mouth, from a viscous liquidto a rubbery solid. While factors such as taste, odor, toxicity,viscosity, cure speed, ease of demolding and strength after cure are allimportant, accuracy is of paramount concern. An impression material mustaccurately replicate the shape, size, and relative locations of bothhard and soft tissues within the mouth. After cure, the impression mustenable casting ("pouring") of an accurate model. The model usually is aplaster of Paris "stone" prepared from an aqueous gypsum slurry, whichafter setting represents a positive mold of the mouth. In recent years,silicones of both the condensation cure and addition cure varieties havebecome widely used as impression materials. They exhibit very goodaccuracy, together with an absence of taste and odor, easy demolding andother properties generally equivalent to or better than othercommonly-used impression materials. However, silicone impressionmaterials suffer from the disadvantage of hydrophobicity. This causesinaccurate impressions in moist fields, and discourages thorough wettingand accurate replication when the model is poured. In an attempt toprovide better wetting of the impression by the gypsum slurry, somedental laboratories spray the cured impression with a detergent solutionjust prior to pouring the model.

Repeated attempts have been made to render silicones more hydrophilic bychemically modifying the siloxane backbone or by appending to thebackbone various functional groups. Typical approaches are described inU.S. Pat. Nos. 4,259,467 (and in many of the references cited therein)and 4,332,922.

Siloxanes have been used as surface active agents, emulsifiers,defoamers or coatings, see, e.g. U.S. Pat. Nos. 3,057,901, 3,398,104,3,402,192, 3,505,377, 3,560,544, 3,929,509, 3,980,688, 4,160,776,4,226,794, 4,337,168, 4,395,454, 4,414,660, 4,431,789, 4,468,491,4,510,227, 4,517,240 and Re. 25,727. Other publications describing theproperties of siloxanes include "Silwet® Surface Active Copolymers"(product literature from Union Carbide Corp., dated October, 1983),"Organomodified Oils [OMO]" (product literature from Union CarbideCorp., dated April, 1982), "UCARSIL® EPS Silicone Hydrophilic Finish"(product literature from Union Carbide Corp., dated March, 1984),"Silicate Cluster™ Fluids (product literature from Olin Corp.), andVick, S.C., "Structure/Property Relationships for SiliconePolyalkyleneoxide Copolymers and Their Effects on Performance inCosmetics", Soap/Cosmetics/Chemical Specialties, 60 (5), 36 (May, 1984).

U.S. Pat. No. 4,354,873 describes an antifouling coating for applicationto submerged boat hulls. The coating contains fumed silica, siliconeoil, antifoulant, and an anionic, nonionic or amphoteric surfactant.

DISCLOSURE OF INVENTION

None of the above patents or publications disclose or suggestcombination of a curable silicone prepolymer and a surfactant. Thepresent invention provides, in one aspect, a curable siliconecomposition comprising a mixture of (a) curable silicone prepolymer and(b) surfactant selected from the group consisting of ethoxylatednonionic surface active agents and cationic or amphoteric fluorochemicalsurface active agents, said surfactant being present in sufficientamount and said ethoxylated nonionic surface active agent (if present)containing sufficient ethyleneoxy groups so that said composition, whencured, has a three minute water contact angle below about 65°. The curedcomposition is readily wet by water, yet retains the other desirableproperties characteristic of silicones. The composition facilitates themaking of more accurate dental impressions and the pouring of moreaccurate models.

The present invention also provides molded hydrophilic silicone articlesprepared by shaping and curing such a composition. Such articles includedental impressions, lithographic plates, release liners, reflectivesheeting, adhesives, coatings and sealants.

In addition, the present invention provides a method for making a dentalimpression, comprising the step of making a negative model of oraltissue using such a composition.

DETAILED DESCRIPTION

In the practice of the present invention, the curable siliconecomposition can be a one-part or multiple-part composition cured by thepresence of adventitious moisture, crosslinking agents, catalysts,and/or heat. Most preferred are two-part addition cure or condensationcure compositions of the room temperature vulcanizing ("RTV") variety.The composition contains a "curable silicone prepolymer", that is, apolysiloxane having one or more functional groups which enable theprepolymer to be polymerized or cured to a state of higher molecularweight. Suitable silicone prepolymers are well-known in the art and aredescribed, for example, in "Silicones", Kirk-Othmer Encyclopedia ofChemical Technology, 3rd Ed., 20, 922-962 (1982), the disclosure ofwhich is incorporated herein hy reference.

The surfactants used in the present invention are selected fromethoxylated nonionic surface active agents (for brevity, these willsometimes be referred to hereafter as "ethoxylated surfactants") andcertain fluorochemical surface active agents (for brevity, these willsometimes be referred to hereafter as "fluorosurfactants"). Includedamong the surfactants useful in the present invention are ethoxylatednonionic surfactants containing perfluoroalkyl groups. These could becalled ethoxylated surfactants or fluorosurfactants. They will bereferred to herein as "ethoxylated surfactants", and the term"fluorosurfactants" will be used to refer to the remainingfluorochemical surfactants used in the present invention. Suchfluorosurfactants are cationic or amphoteric fluorosurfactants.

The surfactant contains one or more solubilizing groups (e.g., one ormore siloxane groups, hydrocarbyl groups or perfluoroalkyl groups) whichrender the surfactant soluble or dispersible in the silicone prepolymer.The surfactant also contains one or more water-loving groups whichrender a cured composition of the invention hydrophilic. When thesurfactant is an ethoxylated surfactant, the water-loving groups areethyleneoxy (--C₂ H₄ O--) groups or hydroxyalkyl-substituted ethyleneoxy(e.g., --CH₂ CH(CH₂ OH)O--) groups. For brevity, these water-lovinggroups will sometimes be collectively referred to hereafter as"ethyleneoxy" groups. When the surfactant is a fluorosurfactant, thewater-loving groups are cationic groups or amphoteric groups, asdescribed in more detail below.

The surfactant is present in a sufficient amount (and if it is anethoxylated surfactant, it contains a sufficient number of ethyleneoxygroups) so that the silicone composition, when cured, has a three minutewater contact angle below about 65°. The term "three minute watercontact angle" refers to the contact angle formed by a drop of distilledwater three minutes after it is applied to a cured composition of theinvention, as measured at room temperature using a goniometer. Suchcontact angle measurements can be made as described in Noll. W.,"Chemistry and Technology of Silicones", 447-452 at 448 (1982).Preferably, such measurements are conducted by curing a composition ofthe invention against a smooth substrate (e.g., a glass sheet),separating the substrate and silicone after cure, and placing the waterdrop on the smooth cured surface of the silicone. Preferably, thecompositions of the invention have a three minute water contact anglebelow about 45°, more preferably below about 30°, and most preferablybelow about 10°.

The measured contact angle appears to be strongly dependent upon theamount of surfactant and, when the wetting agent is an ethoxylatedsurfactant, the number of ethylenoxy groups present within thesurfactant. In general, as the amount of surfactant increases, the watercontact angle decreases. In general, as the number of ethyleneoxy groupsin an ethoxylated surfactant increases beyond one, the water contactangle decreases to a minimum and then increases. The number ofethyleneoxy groups which provides the desired three minute water contactangle will vary depending upon several other factors, including theremaining substituent groups present in the ethoxylated surfactant. Theeffect of such other factors is illustrated in the examples set forthbelow. For example, the water contact angle tends to increase ifpropyleneoxy groups are present in the ethoxylated surfactant.Preferably no propyleneoxy groups are present in such surfactant.

It has also been found that the measured water contact angle increasesif a cured composition is immersed in running water for a prolongedperiod of time. Without intending to be bound by theory, it is believedthat the surfactant is dissolved or dispersed throughout the curedsilicone compositions of the invention and can migrate therein and intoadjacent fluids. When a drop of water is placed on a cured compositionof the invention, it is believed that the surfactant migrates into thedrop and reduces the interfacial surface tension between the water andthe silicone. This hypothesis is supported by the above-noted increasein water contact angle after prolonged water exposure, and by twoadditional observations. First, the measured water contact angle slowlychanges after the drop is placed on the surface of the cured silicone,generally reaching an equilibrium after about five minutes. Second, ifthe drop is observed using an optical comparator (which provides ahighly magnified view of the drop), schlieren patterns become visible atthe interface between the drop and the silicone within a few secondsafter the drop is applied. As this takes place, the schlieren patternsdiffuse throughout the drop and the drop slowly collapses and spreadsout on the surface of the silicone.

In view of the above, the cured compositions of the invention perhapsare best regarded as having semipermanent hydrophilicity, that is, theirhydrophilicity is subject to diminution upon prolonged contact withwater. This dimunition is not a material drawback when making dentalimpressions, since the amount of water or other fluids which will comeinto contact with the impression is not excessive and in any eventsomewhat predictable in advance. A similar observation can be made inregard to other applications for the cured compositions of the invention(e.g., lithographic plates, release liners, reflective sheeting,adhesives, coatings and sealants). Additional applications for thecompositions of the invention such as contact and intraocular lenses,silicone implants (e.g. artificial veins or mammary implants), and wounddressings may be possible, but would be contraindicated somewhat due tothe longer-term fluid exposure involved and the possible adverse effectsof surfactant migration.

Turning now to a more detailed discussion of the ethoxylated surfactant,the ethyleneoxy group(s) can be attached to the solubilizing groupthrough either end of a ethyleneoxy group, that is, through a carbonatom or an oxygen atom of the ethyleneoxy group. Although theethoxylated surfactant can contain as little as one ethyleneoxy group,preferably it contains at least three such groups, more preferably aboutfive to fifteen such groups. The number of ethylenoxy groups should notbe so large that the ethoxylated surfactant becomes waxy, as that mayreduce its effectiveness. The ethoxylated surfactant also can containother groups or substituents, if present in types and amounts which donot interfere with the functioning of such surfactant in the presentinvention or with the curing of the silicone prepolymer. Examples ofsuch groups include propyleneoxy (--C₃ H₆ O--), vinyl, --NH₂, --SH andoxirane groups.

The ethyleneoxy groups are preferably bonded to one another in series,and can be terminated with a hydrogen atom, an alkyl group, one or morepropyleneoxy groups, or a solubilizing group of the type describedabove.

A preferred class of ethoxylated surfactants containing a siloxanesolubilizing group has the average formula ##STR1## where each R isindependently a monovalent hydrocarbyl radical, R¹ is a divalenthydrocarbylene radical, each R² is independently hydrogen or a lowerhydroxyalkyl radical, R³ is hydrogen or a monovalent hydrocarbylradical, x and b are independently greater than or equal to zero, and yand a are independently greater than or equal to one, with the provisothat a has a sufficient value and b is small enough so that a curedcomposition of the invention has the desired three minute water contactangle. Preferably in compounds of Formula I, R and R³ are --CH₃, R¹ is--C₃ H₆ --, R² is hydrogen, x is zero or one, y is one to five, a isfive to 20 and b is zero.

Another preferred class of ethoxylated surfactants has the averageformula ##STR2## where R, R², R³, x, a and b are as defined above.Preferably in compounds of Formula II, R and R³ are --CH₃, R² ishydrogen, a is five to 20 and b is zero.

Ethoxylated surfactants of Formulas I and II above are described in theabove-mentioned Union Carbide Corp. product literature and in U.S. Pat.Nos. 3,505,377, 3,980,688, and 4,431,789, the disclosures of which areincorporated herein by reference. Several of such ethoxylatedsurfactants are available from Union Carbide Corp. as "SILWET" surfaceactive copolymers. Preferred SILWET surface active copolymers includeSILWET L-77, L-7600 and L-7602. SILWET L-77 is an especially preferredethoxylated surfactant. It is believed to have Formula I above, where Rand R³ are --CH₃, R¹ is --C₃ H₆ --, R² is hydrogen, x is zero or one, yis one or two, a is about seven and b is zero.

An additional preferred class of ethoxylated surfactants has the averageformula ##STR3## where R² and R³ are as defined above, each R⁴ group isindependently a monovalent hydrocarbyl radical with the proviso that atleast a majority of the R⁴ groups are sterically hindered alkyl radicalshaving at least three carbon atoms, c is at least four, d is greaterthan or equal to zero, with the further proviso that c has a sufficientvalue and d is small enough so that a cured composition of the inventionhas the desired three minute water contact angle, and T is hydrogen, amonovalent alkyl or alkenyl radical, or a group of the formula--Si(R³)[OSi(OR⁴)₃ ]₂. Preferably in compounds of Formula III, R² ishydrogen, R³ and T are --CH₃, R⁴ is sec-butyl, c is five or more and dis zero. Representative ethoxylated surfactants of Formula III aredescribed in the above-mentioned Olin Corp. product literature and inU.S. Pat. Nos. 4,160,776, 4,226,794, and 4,337,168, the disclosures ofwhich are incorporated herein by reference. At least one such surfactantis experimentally available from Olin Corp. as a "SILFAC"polyethoxylated silicate cluster compound bearing the experimentaldesignation "SILFAC 12M".

An additional preferred class of ethoxylated surfactants has the averageformula

    (R.sup.4 O).sub.3 Si(OC.sub.2 H.sub.3 R.sup.2).sub.e (OC.sub.3 H.sub.6).sub.f OT.sup.1                                   IV

where R² and R⁴ are as defined above, e is at least four, f is greaterthan or equal to zero, with the further proviso that e has a sufficientvalue and f is small enough so that a cured composition of the inventionhas the desired three minute water contact angle, and T¹ is hydrogen, amonovalent alkyl or alkenyl radical, or a group of the formula--Si(OR⁴)₃. Such ethoxylated surfactants are believed to be novel andtheir preparation is described in more detail below. Preferably incompounds of Formula IV, R² is hydrogen, R⁴ is sec-butyl, e is ten to20, f is zero and T¹ is --Si(sec-butoxy)₃.

Suitable ethoxylated surfactants containing hydrocarbyl solubilizinggroups are shown in "Surfactants and Detersive Systems", Kirk-OthmerEncyclopedia of Chemical Technology, 3rd Ed., 22, 360-377 (1983), thedisclosure of which is incorporated herein by reference. A preferredclass of such ethoxylated surfactants has the average formula

    R.sup.5 --(OC.sub.2 H.sub.3 R.sup.2).sub.g OH].sub.1 to 3  V

where R² is as defined above, R⁵ is a saturated or unsaturated alkyl oralkylphenyl radical having at least seven carbon atoms, and g has asufficient value so that a cured composition of the invention has thedesired three minute water contact angle. Preferably in compounds ofFormula V, R⁵ is alkyl and g is at least about five.

Suitable ethoxylated surfactants containing perfluoroalkyl solubilizinggroups are described in U.S. Pat. No. 2,915,544, the disclosure of whichis incorporated herein by reference. A preferred class of suchethoxylated surfactants has the average formula

    Rf--Q(C.sub.2 H.sub.3 R.sup.2 O).sub.h (C.sub.3 H.sub.6 O).sub.i R.sup.3 ].sub.1 or 2                                              VI

where R² and R³ are as defined above, Rf is a fluorinated, monovalent ordivalent, aliphatic, preferably saturated organic radical containing atleast four carbon atoms and at least a terminal perfluoromethyl group, Qis a polyvalent (e.g., divalent) hydrocarbylene linking group (e.g.,--C₂ H₄ --, or --SO₂ NR-- where R is as defined above), h is greaterthan or equal to one, and i is greater than or equal to zero, with theproviso that h has a sufficient value and i is small enough so that acured composition of the invention has the desired three minute watercontact angle.

The surfactant used in the present invention can also be a cationic oramphoteric fluorosurfactant. Such fluorosurfactants contain at least oneperfluoroalkyl solubilizing group Rf where Rf is as defined above. Thecationic fluorosurfactants contain at least one cationogenic group whichis the radical of a base having an ionization constant in water at 25°C. of at least about 10⁻⁶. The amphoteric fluorosurfactants contain atleast one such cationogenic group and at least one anionogenic groupwhich is the radical of an acid having an ionization constant in waterat 25° C. of at least about 10⁻⁶. Suitable fluorosurfactants aredescribed, for example, in U.S. Pat. No. 4,484,990, the disclosure ofwhich is incorporated herein by reference.

The compositions of the invention contain sufficient surfactant so thata cured composition of the invention has the desired three minute watercontact angle. As pointed out above, when the amount of surfactant isincreased, the three minute water contact angle generally decreases. Asthe amount of surfactant is increased further, the three minute contactangle reaches a minimum threshold value which does not decreasesignificantly with the use of additional surfactant. In general, apreferred amount of surfactant is an amount sufficient to provide athree minute water contact angle having such minimum threshold value.This preferred amount of surfactant also depends upon the particularcurable silicone prepolymer chosen, the particular surfactant chosen,and the amounts and types of other adjuvants present in the compositionsof the invention. Expressed on a weight basis, an effective amount ofsurfactant preferably is below about 30 weight percent, based on thetotal weight of the composition. More preferably, the amount ofsurfactant is about 0.25 to five weight percent, and most preferablyabout 0.5 to two weight percent.

The compositions of the invention are mixed, packaged and stored likeconventional curable silicone compositions. In two-part compositions,the surfactant usually can be present in either part of the composition,or in both parts of the composition. However, where the surfactant maytend to react with either part of the composition (e g., if thesurfactant contains one or more Si-H groups, and will be used in anaddition cure polysiloxane), then the surfactant should be added only toa part of the composition with which it will not itself react. Mixturesof more than one surfactant can be used if desired.

The compositions of the invention can also contain adjuvants of the typecustomarily employed in curable silicone compositions. Such adjuvantsinclude crosslinking agents, catalysts, fillers, pigments, reinforcingagents, plasticizers and the like.

The invention is illustrated in the following examples, in which allparts and percentages are by weight unless otherwise indicated. Becausethe examples are merely illustrative, they are not to be construed aslimiting the scope of the invention.

EXAMPLE 1

Several surfactants were evaluated in a two-part vinylpolysiloxaneimpression material of the following formulation:

    ______________________________________                                        Catalyst part:                                                                Vinyl-terminated polydimethylsiloxane, M.sub.n = 24,000                                                   46.3%                                             Silicone-treated silica.sup.(1)                                                                           6.1                                               Ground silica.sup.(2)       46.9                                              Catalyst made from a 2:1 mixture of 1,3-divinyl                                                           0.7                                               tetramethyl disiloxane and chloroplatinic acid                                Base part:                                                                    Vinyl-terminated polydimethylsiloxane, M.sub.n = 24,000                                                   42.4%                                             Silicone-treated silica.sup.(1)                                                                           7.3                                               Ground silica.sup.(2)       46.6                                              Silicone crosslinking agent.sup.(3)                                                                       3.7                                               Tetravinyltetramethylcyclotetrasiloxane                                                                   0.06                                              ______________________________________                                         .sup.(1) "QUSO 545", Philadelphia Quartz.                                     .sup.(2) "IMSIL A25", Illinois Minerals.                                      .sup.(3) A copolymer which on the basis of monomers charged would have an     average composition MD'.sub.10 D.sub.21 M where                               M = Si(CH.sub.3).sub.3 O.sub.0.5                                              D = Si(CH.sub.3).sub.2 O                                                      D' = Si(CH.sub.3)HO.                                                     

Each surfactant was added at a level of one percent (and in one instancetwo percent) to both parts of the above formulation. The two parts werethen combined in equal proportions, mixed rapidly, poured into acylindrical metal mold 19 mm in diameter×1 mm in thickness sandwichedbetween two glass microscope slides, and allowed to cure for ten minutesat room temperature. A drop of distilled water was carefully placed onthe cured surface and the contact angle formed by the drop was measuredusing a goniometer 30 seconds and three minutes after placement of thewater drop. Set out below in TABLE I are the run number, surfactant, andmeasured water contact angles for each composition.

                                      TABLE I                                     __________________________________________________________________________                                            Water contact angle                   Run no.                                                                            Surfactant                         30 sec.                                                                            3 min.                           __________________________________________________________________________    1    None (control)                     100°                                                                        99°                       2    Polyalkylene oxide modified polymethylsiloxane                                                                    9°                                                                          6°                            ("Silwet L-77", Union Carbide Corp.)                                     3    Polyalkylene oxide modified polymethylsiloxane                                                                   97°                                                                         60°                            ("Silwet L-7600", Union Carbide Corp.)                                   4    Polyalkylene oxide modified polymethylsiloxane                                                                   92°                                                                         60°                            ("Silwet L-7602", Union Carbide Corp.)                                   5    [(sec-butoxy).sub.3 SiO].sub.2 Si(CH.sub.3)(OC.sub.2 H.sub.4).sub.12          OCH.sub.3 ("SILFAC 12M", Olin Corp.)                                                                             36°                                                                         22°                       6    Polyethoxylated fatty alcohol ("Emulphor AM-310", GAF)                                                           33°                                                                         28°                       7    (H.sub.3 C).sub.3 CCH.sub.2 C(CH.sub.3).sub.2 C.sub.6 H.sub.4                 (OC.sub.2 H.sub.4).sub.9-10 OH ("Triton X-100", Rohm &                                                           81°                                                                         64°                       8    C.sub.9 H.sub.19 C.sub.6 H.sub.4 O(C.sub.2 H.sub.4).sub.9-10 OH               ("Igepal CO-630", GAF)             68°                                                                         46°                       9    Butoxypolypropyleneoxypolyethyleneoxyethanol ("Tergitol                                                          55°                                                                         50°                            Union Carbide Corp.).sup. (1)                                            10   C.sub.8 F.sub.17 SO.sub.2 N(C.sub.2 H.sub.5)C.sub.2 H.sub.4 O(C.sub.3          H.sub.6 O).sub.8 H                60°                                                                         55°                       11   C.sub.8 F.sub.17 SO.sub.2 N(C.sub.2 H.sub.5)(C.sub.2 H.sub.4                  O).sub.7 H                         29°                                                                         20°                       12   C.sub.8 F.sub.17 SO.sub.2 N(C.sub.2 H.sub.5)(C.sub.2 H.sub.4                  O).sub.14 H                        78°                                                                         26°                       13   C.sub.8 F.sub.17 SO.sub.2 NHC.sub.3 H.sub.6 N.sup.+ (CH.sub.3).sub.3          I.sup.-                            102°                                                                        40°                       14   C.sub.6 F.sub.13 SO.sub.2 N(CH.sub.2 CHOHCH.sub.2 SO.sub.3.sup.-)C.su         b.3 H.sub.6 N.sup.+ (CH.sub.3).sub.2 C.sub.2 H.sub.4 OH.sup.(2)                                                  72°                                                                         64°                       15   C.sub.8 F.sub.17 SO.sub.2 N(C.sub.2 H.sub.5)(CH.sub.2).sub.2                  OCO(CH.sub.2).sub.2 NH(CH.sub.2).sub.3 Si(OCH.sub.3).sub.3                                                       82°                                                                         63°                       __________________________________________________________________________     .sup.(1) Evaluated at two percent surfactant instead of at one percent.       When evaluated at one percent, the 30 second water contact angle was          86° and the three minute water contact angle was 76°.           .sup.(2) Evaluated at one % solids, using a 25 percent solution in C.sub.     H.sub.9 OC.sub.2 H.sub.4 OC.sub.2 H.sub.4 OH.                            

This example shows the useful improvement in water wettability obtainedusing the compositions of the invention. The composition of Run no. 2was particularly effective. Slow cure (set) times were observed for thecompositions of Run Nos. 9, 13 and 15.

COMPARATIVE EXAMPLE 1

One percent (and in one instance ten percent) additions of severalcomparison materials were evaluated in the impression materialformulation of EXAMPLE 1. Set out below in TABLE II are the run number,comparison material, and measured water contact angles for eachcomposition.

                                      TABLE II                                    __________________________________________________________________________                                          Water contact angle                     Run no.                                                                            Comparison material              30 sec.                                                                            3 min.                             __________________________________________________________________________    1    Polyalkylene oxide modified polymethylsiloxane                                                                 94°                                                                         90°                              ("Silwet L-720", Union Carbide Corp.)                                    2    Polyalkylene oxide modified polymethylsiloxane                                                                 97°                                                                         97°                              ("Silwet L-7002", Union Carbide Corp.)                                   3    CH.sub.3 Si[OSi(sec-butoxy).sub.3 ].sub.3 ("Silicate Cluster 102",            Olin Corp.)                      --    105°.sup.(1)               4    CH.sub.3 (OC.sub.2 H.sub.4).sub.7.2 OH                                                                         --     76°.sup.(1)               5    CH.sub.3 (OC.sub.2 H.sub.4).sub.7.2 OH.sup.(2)                                                                 --     76°.sup.(1)               6    Sodium lauryl sulfate ("Duponol ME", E.I. duPont de Nemours &                                                  91°                                                                         88°                         7    Organic phosphate ester, free acid ("Gafac PE-510", GAF                                                        89°                                                                         74°                         8    Fatty amide ("Antaron FC-34", GAF Corp.)                                                                       90°                                                                         82°                         9    30:70 Copolymer of C.sub.8 F.sub.17 SO.sub.2 N(CH.sub.3)C.sub.2               H.sub.4 OCOC(CH.sub.3)═CH.sub.2 and                                                                        103°                                                                        101°                        10   C.sub.8 F.sub.17 SO.sub.3 K      89°                                                                         88°                         11   C.sub.7 F.sub.15 COONH.sub.4     90°                                                                         85°                         __________________________________________________________________________     .sup.(1) Water contact angle measured at equilibrium. The three minute        water contact angle would be the same or only slightly different.             .sup.(2) Evaluated at ten percent comparison material rather than one         percent.                                                                 

This example shows several comparison materials which did not providethe desired water contact angle. The materials of Run nos. 1 and 2 didnot have a sufficient number of ethyleneoxy groups or had too manypropyleneoxy groups. The materials of Run nos. 3, 6 through 8, 10 and 11were not ethoxylated surfactants, cationic fluorosurfactants, oramphoteric fluorosurfactants. The material of Run nos. 4 and 5 did nothave an appropriate solubilizing group. The material of Run no. 9 was awaxy solid.

EXAMPLE 2

A conventional two-part condensation cure silicone impression material("Citricon" Dental Impression Resin, Kerr Division of Sybron Corp.) wasmade hydrophilic by the addition of one percent [(sec-butoxy)₃ SiO]₂Si(CH₃)(OC₂ H₄)₁₂ OCH₃ to each part. The three minute water contactangle was reduced from 98° without surfactant to 28° with surfactant.

EXAMPLE 3

Varying amounts of [(sec-butoxy)₃ SiO]₂ Si(CH₃)(OC₂ H₄)₁₂ OCH₃ wereadded to both parts of the impression material formulation of EXAMPLE 1.The resulting compositions were cured and evaluated using the method ofEXAMPLE 1, with water contact angles being measured at equilibriumrather than at three minutes. The water contact angles at three minutestypically would be the same or only slightly different. Set out below inTABLE III are the run number, percent surfactant, and equilibrium watercontact angle for each composition.

                  TABLE III                                                       ______________________________________                                                               Equilibrium water                                      Run no.     % Surfactant                                                                             contact angle                                          ______________________________________                                        1           0          100°                                            2           0.125      102°                                            3           0.25       48°                                             4           0.5        34°                                             5           1.0        32°                                             6           2.0        27°                                             7           15.0       26°                                             8           30.0       21°                                             ______________________________________                                    

This example illustrates the effect of variation in the amount ofsurfactant.

EXAMPLE 4

The composition of Run no. 6 of EXAMPLE 3 was cured in a two mm deepsplit mold made by stacking two of the one mm deep molds used in EXAMPLE3. After curing the composition, the upper half of the mold was removedand the cured composition then sliced in half at the mold parting lineusing a razor blade. A water contact angle measurement was quicklyperformed on a sliced surface of the sample. At equilibrium, its watercontact angle was 25°, compared to 27° tor Run no. 6 of EXAMPLE 3.

This example illustrates that the interior of a cured composition of theinvention is hydrophilic.

EXAMPLE 5

Varying amounts of the ethoxylated surfactant "Silwet L-77" were addedto both parts of the impression material formulation of EXAMPLE 1. Theresulting compositions were cured and evaluated using the method ofEXAMPLE 1. Set out below in TABLE IV are the run number, percentsurfactant, and three minute water contact angle for each composition.

                  TABLE IV                                                        ______________________________________                                                               3 Minute water                                         Run no.     % Surfactant                                                                             contact angle                                          ______________________________________                                        1           0          100°                                            2           0.25       67°                                             3           0.50       45°                                             4           0.75       12°                                             5           1.00        9°                                             ______________________________________                                    

This example also illustrates the effect of variation in the amount ofsurfactant.

EXAMPLE 6

A series of silicate "cluster" surfactants having the following averageformula were synthesized using the method shown in Example 1 of U.S.Pat. No. 4,226,794: ##STR4##

One percent of each of these surfactants was added to both parts of theimpression material formulation of EXAMPLE 1. Set out below in TABLE Vare the run number, identity of R and n, and the equilibrium watercontact angle for each composition.

                  TABLE V                                                         ______________________________________                                                                      Equilibrium water                               Run no.   R            n      contact angle                                   ______________________________________                                        1         H--          13.2   52°                                      2         CH.sub.3 --  3.0    92°                                      3         CH.sub.3 --  8.7    65°                                      4         CH.sub.3 --  13.2   56°                                      5         CH.sub.2 ═CH--                                                                         13.2   66°                                      6         CH.sub.2 ═CH--                                                                         34.6   59°                                      ______________________________________                                    

An additional series of silicate "cluster" surfactants of the followingaverage formula was synthesized using the method shown in Example 2 ofU.S. Pat. No. 4.160,776: ##STR5##

One percent of each of these surfactants was added to both parts of theimpression material formulation of EXAMPLE 1. Set out below in TABLE VIare the run number, identity of R and n, and the equilibrium watercontact angle for each composition.

                  TABLE VI                                                        ______________________________________                                                                      Equilibrium water                               Run no.   R            n      contact angle                                   ______________________________________                                        1         H--          7.2    39°                                      2         CH.sub.3 --  7.2    31°                                      3         CH.sub.3 --  11.8   32°                                      4         CH.sub.3 --  16.3   37°                                      5         CH.sub.2 ═CH--                                                                         2.0    88°                                      6         CH.sub.2 ═CH--                                                                         7.2    49°                                      7         CH.sub.2 ═CH--                                                                         11.8   28°                                      8         CH.sub.2 ═CH--                                                                         42.5   100°                                     ______________________________________                                    

This example shows the effect variations in structure have upon thehydrophilicity of a cured composition of the invention.

EXAMPLE 7

Tri(sec-butoxy)chlorosilane was prepared according to the proceduredescribed in Schott, G., Englebrecht, L., and Holdt, H. J., Z. anorg.allg. Chem., 459, 177-186 (1979). A 56.5 g portion of the resultingproduct was added dropwise to a stirred solution of 60 g of apolyethyleneglycol having the average formula HO(C₂ H₄ O)₁₃.2 H("Carbowax 600", Union Carbide Corp.) and 16 g pyridine in 300 mltoluene. The resulting mixture was heated to 70° C. for two hours, thenallowed to cool to room temperature and filtered to remove pyridinehydrochloride. Toluene was removed from the mixture using a rotaryevaporator. Final traces of toluene and unreacted pyridine were removedunder high vacuum (10⁻² Torr). The product was a clear, colorless tofaint yellow fluid. NMR and IR analyses were consistent with the averagestructure (sec-butoxy)₃ SiO(C₂ H₄ O)₁₃.2 Si(sec-butoxy)₃. Using ¹ H NMRanalysis with CDCl₃ as solvent, delta values were 0.90(18H,d,--CHCH₃),1.17 (18H,t,--CH₂ CH₃), 1.45 (12H,q,--CH₂ CH₃), 3.61 (53H,s,OCH₂ CH₂),and 3.87 (6H,--CH). Using IR analysis, absorption peaks occurred at2898, 1485, 1379, 1351, 1330, 1299, 1258, 1117, 1058, 1018, 960, 862,816 and 735 cm⁻¹.

When one percent of this novel ethoxylated surfactant was added to bothparts of the impression material formulation of EXAMPLE 1, the curedcomposition had 30 second and three minute water contact angles of 44°and 32°, respectively.

EXAMPLE 8

Using the method of EXAMPLE 7, and substituting a variety of alkoxylatedlinear alcohols or diols for the polyethyleneglycol used in EXAMPLE 7, aseries of novel alkoxylated surfactants having the average formula (R⁴O)₃ Si(OC₂ H₄)_(e) (OC₃ H₆)_(f) OT¹ were synthesized. Using the methodof EXAMPLE 1, one percent of each of these surfactants was added to bothparts of the impression material formulation of EXAMPLE 1. Set out belowin TABLE VII are the run number, identity of R⁴, e, f and T¹ and theequilibrium water contact angle for each composition.

                  TABLE VII                                                       ______________________________________                                                                            Equilibrium water                         Run no.                                                                              R.sup.4   e      f     T.sup.1                                                                             contact angle                             ______________________________________                                         1     sec-butyl 2      0     --CH.sub.3                                                                          90°                                 2     sec-butyl 7.2    0     --CH.sub.3                                                                          56°                                 3     sec-butyl 11.8   0     --CH.sub.3                                                                          72°                                 4     sec-butyl 16.3   0     --CH.sub.3                                                                          84°                                 5     sec-butyl 42.5   0     --CH.sub.3                                                                          98°                                 6     sec-butyl 3      0     T'.sup.(1)                                                                          76°                                 7     sec-butyl 6.4    0     T'    63°                                 8     sec-butyl 8.7    0     T'    57°                                 9     sec-butyl 13.2   0     T'    36°                                10     sec-butyl 22.3   0     T'    59°                                11     sec-butyl 0      16.9  T'    71°                                12     sec-butyl 0      18.8  T'    66°                                13     sec-butyl 0      34.2  T'    73°                                14     sec-butyl 0      51.4  T'    76°                                15     .sup.(2)  7.2    0     --CH.sub.3                                                                          44°                                16     .sup.(2)  16.3   0     --CH.sub.3                                                                          59°                                17     .sup.(2)  13.2   0     T".sup.(3)                                                                          85°                                18     .sup.(2)  22.3   0     T"    76°                                ______________________________________                                         .sup.(1) T' = --Si(secbutoxy).sub.3.                                          .sup.(2) Two secbutoxy groups and one allyloxy group were attached to the     Si atom shown in the formula.                                                 .sup.(3) T' = --Si(secbutoxy).sub.2 (allyloxy).                          

This example shows several novel surfactants, and the effect variationin their structure has upon the hydrophilicity of a cured composition ofthe invention.

EXAMPLE 9

Three curable silicone compositions were formulated as in EXAMPLE 1,using one percent [(sec-butoxy)₂ SiO]₂ Si(CH₃)(OC₂ H₄)₁₂ OCH₃ in thecatalyst portion, base portion or both portions of the formulation. Thecure time of each composition was measured at 24° C. (using a "Monsanto"oscillating disk rheometer) immediately after preparing thecompositions, and after aging the compositions for seven days at 60° C.The results are set out below in TABLE VIII.

                  TABLE VIII                                                      ______________________________________                                        Surfactant added to                                                                          Cure time, minutes:seconds                                     Catalyst  Base     Unaged   Aged 7 days @ 60° C.                       ______________________________________                                        No        No       .sup. 5:15.sup.(1)                                                                     .sup. 4:45.sup.(1)                                Yes       No       5:00     4:55                                              No        Yes      4:34     4:30                                              Yes       Yes      4:55     4:50                                              ______________________________________                                         .sup.(1) Average of several runs.                                        

Comparable results were obtained when this example was repeated usingthe ethoxylated surfactant "Silwet L-77".

This example demonstrates the excellent storage stability which can beobtained with these compositions.

EXAMPLE 10

The composition of Run no. 5 of EXAMPLE 1 was prepared without silicafillers. The equilibrium water contact angle of the cured compositionwas 28°, compared to 32° when fillers were included.

This example illustrates that the use of filler did not materiallyaffect hydrophilicity.

EXAMPLE 11

The composition of Run no. 1 of EXAMPLE 5 was cured and washed in coldrunning tap water for two days. The measured water contact angle (asobserved using an optical comparator) increased from 20°-23° beforewashing to 60°-63° after washing. Schlieren patterns could be observedwithin the water drop when it was placed on the cured silicone surface.This example indicates that the surfactant may have migrated from thesilicone into the wash water and into the water drop.

EXAMPLE 12

The composition of Run no 1 of EXAMPLE 5 was extruded in a thin streaminto a tray of water. The extrudate tended to maintain its shapeunderwater. A composition prepared without surfactant tended to"ball-up" underwater, perhaps in order to minimize its exposed surfacearea. This example indicates that the compositions of the invention mayyield impressions with improved accuracy in submerged fields, such asimpressions of the gingival sulcus made in the presence of crevicularfluids.

EXAMPLE 13

The composition ot Run no. 4 of EXAMPLE 5 was used to make an impressionot a qrooved aluminum block according to the procedure of AmericanDental Association Specification No. 19. The composition produced anexcellent impression which passed the specification. It also passed ifthe aluminum block was flooded with water before taking the impression.A composition prepared without surfactant passed if the aluminum blockwas dry but failed if the block was wet.

EXAMPLE 14

Several silicone impression material formulations and comparisonpolyether impression material formulations were cast in a rectangularprismatic mold to form a cast bar 57 mm long×20 mm wide×four mm thick.The mold had been previously scribed with two marks across its longdimension, spaced 50 mm apart. These marks were reproduced in the castbar. Each bar stored at room temperature and 32 percent or 100 percentrelative humidity for 24 hours, then removed and measured to determineif the spacing between the scribed marks had changed. Set out below inTABLE IX are the run number, impression material, and the measureddimensional change at each relative humidity.

                  TABLE IX                                                        ______________________________________                                                         Dimensional change                                           Run no. Impression material                                                                          32% R.H.   100% R.H.                                   ______________________________________                                        1       Control.sup.(1)                                                                              +0.02%     +0.21%                                      2       Control +0.75% -0.07%     +0.22%                                              "Silwet L-77".sup.(2)                                                 3       Polyether.sup.(3)                                                                            +0.08%     +0.64%                                      4       Polyether.sup.(4)                                                                            -0.04%     +0.75%                                      ______________________________________                                         .sup.(1) A composition like that of Run no. 1 of EXAMPLE 1 but containing     in the catalyst part 42.4% vinylterminated polydimethylsiloxane, 4.4%         siliconetreated silica, 50.6% ground silica, 0.6% catalyst, and 2.1%          pigment, and containing in the base part 37.8% vinyl terminated               polydimethyldisiloxane, 4.4% siliconetreated silica, 52.4% ground silica,     2.7% silicone crosslinker of average composition MD'.sub.6.8 D.sub.10 M,      0.7% silicone crosslinker of average composition MD'.sub.10 D.sub.21 M, 2     pigment, and 0.03% tetravinyltetramethylcyclotetrasiloxane. Average of tw     samples.                                                                      .sup.(2) Average of three samples.                                            .sup.(3) "Impregum Impression Material Type 1", Premier Dental Products.      .sup.(4) "Polyjel", L. D. Caulk Company.                                 

This example illustrates the excellent dimensional stability ofcompositions of the invention even when stored under conditions of highhumidity.

EXAMPLE 15

A two-part impression material formulation was prepared from thefollowing ingredients:

    ______________________________________                                        Catalyst part:                                                                Vinyl-terminated polydimethylsiloxane, M.sub.n = 70,000                                                   15.0%                                             Vinyl-terminated polydimethylsiloxane, M.sub.n = 24,000                                                   6.4                                               Silicone-treated silica     2.7                                               Ground silica               33.0                                              Calcium carbonate.sup.(1)   35.7                                              Catalyst                    0.15                                              Ethoxylated surfactant.sup.(2)                                                                            0.5                                               White mineral oil, USP      6.5                                               Base part:                                                                    Vinyl-terminated polydimethylsiloxane, M.sub.n = 70,000                                                   12.1%                                             Vinyl-terminated polydimethylsiloxane, M.sub.n = 24,000                                                   5.2                                               Silicone-treated silica     2.7                                               Ground silica               33.7                                              Calcium carbonate.sup.(1)   36.4                                              Silicone crosslinker.sup.(3)                                                                              2.0                                               Pigment                     0.6                                               Ethoxylated surfactant.sup.(2)                                                                            0.75                                              ______________________________________                                         .sup.(1) "Vicron", Pfizer Corp.                                               .sup.(2) "Silwet L77".                                                        .sup.(3) Copolymer of average composition MD'.sub.6.8 D.sub.10 M.        

This composition was used to make impressions of the oral tissue of tenpatients. Most patients could detect a slight taste, but none found itobjectionable. Those patients that noticed a taste judged it to be muchbetter than the taste of rubber-base or polyether impression materials.An additional impression was made of the oral tissue of a patient whohad previously experienced a severe allergic reaction to a commercialpolyether impression material. She detected no taste and did notexperience any allergic reaction of other adverse symptoms.

EXAMPLE 16

A two-part impression material formulation was prepared from thefollowing ingredients:

    ______________________________________                                        Catalyst part:                                                                Vinyl-terminated polydimethyldixiloxane, Mn = 24,000                                                      41.4%                                             Silicone-treated silica     4.3                                               Ground silica               52.7                                              Ethoxylated surfactant.sup.(1)                                                                            0.75                                              Catalyst                    3.0                                               Pigment                     0.5                                               Base part:                                                                    Vinyl-terminated polydimethylsiloxane, Mn = 24,000                                                        30.0%                                             Silicone-treated silica     4.4                                               Ground silica               54.1                                              Silicone crosslinker.sup.(2)                                                                              7.3                                               Pigment                     0.35                                              Ethoxylated surfactant.sup.(1)                                                                            0.75                                              ______________________________________                                         .sup.(1) "Silwet L77".                                                        .sup.(2) Copolymer of average composition MD'.sub.6.8 D.sub.10 M.        

This composition was used to make impressions of the oral tissue ofthree pateints. Excellent detail reproduction was obtained.

EXAMPLE 17

A typical full crown preparation was made on the upper left lateralincisor of a "Typodont" dental model. Two custom impression trays wereprepared by lining the trays with the hydrophilic impression material ofEXAMPLE 15 or with a corresponding non-hydrophilic impression materialprepared without ethoxylated surfactant. Two final impressions weretaken by lining these custom trays with the hydrophilic impressionmaterial of Run No. 5 of EXAMPLE 1 or with the non-hydrophilicimpression material of Run No. 1 of EXAMPLE 1, respectively. Models ofthe cured impressions were poured using "Vel-Mix Stone" (Kerr Divisionof Sybron Corp.). The model made from the hydrophilic impressionmaterials was evaluated by three consulting dentists, and regarded byeach as superior to the model made from the non-hydrophilic impressionmaterials, especially in detail reproduction.

Comparable results were obtained when this example was repeated bytaking impressions of the oral tissue of several human patients. Theobserved superiority of the models made from the hydrophilic impressionmaterials was especially apparent for impressions made under moist fieldconditions.

Various modifications and alterations of this invention will be apparentto those skilled in the art without departing from the scope and spiritof this invention and the latter should not be restricted to that setforth herein for illustrative purposes.

We claim:
 1. A curable silicone composition comprising a mixture of (a)curable silicone prepolymer and (b) surfactant selected from the groupconsisting of (i) ethoxylated nonionic surface active agents containingone or more siloxane or perfluoroalkyl solubilizing groups and (ii)cationic or amphoteric fluorochemical surface active agents, saidsurfactant being present in sufficient amount and said ethoxylatednonionic surface active agent, if present, containing sufficientethyleneoxy groups so that said composition, when cured, has a threeminute water contact angle below about 65°.
 2. A composition accordingto claim 1, wherein said curable silicone prepolymer comprises atwo-part RTV addition cure or condensation cure polysiloxane.
 3. Acomposition according to claim 1, wherein said surfactant comprises saidethoxylated nonionic surface active agent.
 4. A composition according toclaim 3, wherein said agent contains at least three unsubstituted orhydroxyalkyl-substituted ethyleneoxy groups.
 5. A composition accordingto claim 4, wherein said agent contains about five to fifteenunsubstituted ethyleneoxy groups.
 6. A composition according to claim 3,comprising surfactant having the following average formulas I or II:##STR6## wherein each R is independently a monovalent hydrocarbylradical, R¹ is a divalent hydrocarbylene radical, each R² isindependently hydrogen or a lower hydroxyalkyl radical, R³ is hydrogenor a monovalent hydrocarbyl radical, x and b are independently greaterthan or equal to zero, and y and a are independently greater than orequal to one, with the proviso that a has a sufficient value and b issmall enough so that said composition, when cured, has a three minutewater contact angle below about 65°.
 7. A composition according to claim6, wherein R and R³ are --CH₃, R¹ is --C₃ H₆ --, R² is hydrogen, x iszero or one, y is one to five, a is five to 20 and b is zero.
 8. Acomposition according to claim 7, wherein said curable siliconeprepolymer comprises a two part RTV addition cure polysiloxane, saidsurfactant has said formula I, y is one or two, a is about seven, andsaid contact angle is below about 30°.
 9. A composition according toclaim 3, wherein said surfactant has the average formula ##STR7##wherein each R² is independently hydrogen or a lower hydroxyalkylradical, R³ is hydrogen or a monovalent hydrocarbyl radical, each R⁴group is independently a monovalent hydrocarbyl radical with the provisothat at least a majority of the R⁴ groups are sterically hindered alkylradicals having at least three carbon atoms, c is at least 4, d isgreater than or equal to zero with the further proviso that c has asufficient value and d is small enough so that said composition, whencured, has a three minute water contact angle below about 65° , and T isa monovalent alkyl or alkenyl radical or a group of the formula--Si(R²)[OSi(OR⁴)₃ ]₂.
 10. A composition according to claim 9, whereincurable silicone prepolymer comprises a two part RTV addition curepolysiloxane, R² is hydrogen, R³ and T are --CH₃, R⁴ is sec-butyl, c is5 or more, d is zero, and said contact angle is below about 45°.
 11. Acomposition according to claim 3, wherein said surfactant has theaverage formula

    Rf--Q(C.sub.2 H.sub.3 R.sup.2 O).sub.h (C.sub.3 H.sub.6 O).sub.i R.sup.3 ].sub.1 or 2

wherein Rf is a fluorinated, monovalent or divalent, aliphatic organicradical containing at least four carbon atoms and at least a terminalperfluoromethyl group, Q is a polyvalent hydrocarbylene linking group,each R² is independently hydrogen or a lower hydroxyalkyl radical, R³ ishydrogen or a monovalent hydrocarbyl radical, h is greater than or equalto one, and i is greater than or equal to zero, with the proviso that hhas a sufficient value and i is small enough so that said composition,when cured, has a three minute water contact angle below about 65°. 12.A composition according to claim 1, wherein said surfactant comprisessaid fluorochemical surface active agent.
 13. A cured siliconecomposition, comprising polysiloxane polymer having dissolved ordispersed therein surfactant selected from the group consisting of (a)ethoxylated nonionic surface active agents containing one or moresiloxane or perfluoroalkyl solubilizing groups and (b) cationic oramphoteric fluorochemical surface active agents, said surfactant beingpresent in sufficient amount and said ethoxylated nonionic surfaceactive agent, if present, containing sufficient ethyleneoxy groups sothat said composition has a three minute water contact angle below about65°, said composition having semipermanent hydrophilicity.
 14. Acomposition according to claim 13, in the form of a dental impressioncomprising a negative mold of oral tissue.
 15. A composition accordingto claim 14, wherein said impression has a three minute water contactangle below about 45°.
 16. A composition according to claim 13, in theform of a lithographic plate, release liner, reflective sheet, adhesive,coating or sealant.
 17. A method for making a dental impression,comprising the step of making a negative mold or orgal tissue using assaid mold a curable silicone composition comprising a mixture of (a) RTVaddition cure or condensation cure polysiloxane prepolymer and (b)surfactant selected from the group consisting of (i) ethoxylatednonionic surface active agents containing one or more siloxane orperfluoroalkyl solubilizing groups and (ii) cationic or amphotericfluorochemical surface active agents, said surfactant being present insufficient amount and said ethoxylated nonionic surface active agent, ifpresent, containing sufficient ethyleneoxy groups so that saidcomposition, when cured, has a three minute water contact angle belowabout 65°.
 18. A method according to claim 17, wherein said surfactanthas the average formula ##STR8##